TWI395440B - Multi-carrier receiver with dynamic power adjustment and method for dynamically adjusting the power consumption of a multi-carrier receiver - Google Patents

Description

Multi-carrier receiver with dynamic power adjustment and method for dynamically adjusting power consumption of multi-carrier receiver

The present invention relates to receiving multi-carrier signals, and more particularly to a multi-carrier receiver with dynamic power adjustment and a method of dynamically adjusting the power consumption of a multi-carrier receiver.

Multi-carrier modulation methods, such as orthogonal frequency division multiplexing (hereinafter referred to as OFDM), are now widely used. OFDM is a modulation method designed in the 1970s to use multiple different subcarriers to transmit multiple symbols in parallel. The OFDM system forms its symbols by k complex Quadrature Amplitude Modulation (QAM) symbols X _k , each subcarrier has a frequency Where T _u is the subcarrier symbol period. Each OFDM subcarrier is displayed in the frequency domain Spectrum. By spacing 2N+1 subcarriers from each other in the frequency domain The primary peak of the sinc(x) spectrum of each subcarrier coincides with the zero value of any other subcarrier. Thus, although the spectrum of the subcarriers overlaps, the subcarriers are still orthogonal to each other. OFDM is well known as a highly efficient spectrum transmission architecture capable of handling channel impairments occurring in wireless environments. The basic starting point for OFDM is to split the available spectrum into multiple subchannels (subcarriers). The subcarriers are subjected to almost flat fading by setting all of the subcarrier narrow bands, thereby simplifying the equalization.

However, mobile reception is still a problem associated with OFDM systems. The mobile receiver will experience a Doppler shift that will compromise the orthogonality between each subcarrier, thereby reducing system performance. In this case, since signal components from one subcarrier interfere with signal components from other subcarriers (usually adjacent subcarriers), inter-carrier interference (hereinafter referred to as ICI) occurs. Mobile receivers also encounter problems with time-varying channels. Time-varying channels also limit the effectiveness of the system. Typically, ICI cancellers are used to compensate for ICI, and additional long interleaver with forward error correction capability is used to improve system performance. For example, Digital Video Broadcast Hand-held (hereinafter referred to as DVB-H) specifies multiprotocol encapsulation forward error correction (hereinafter referred to as MPE-FEC). ) to provide an additional layer of interleaving and error correction to provide a more stable signal in the mobile environment.

Although the ICI canceller and MPE-FEC can improve the performance of the system, these two features also consume more power. Since handheld devices typically have limited power, system designers must compromise between system performance and power consumption.

The present invention provides a method for multi-carrier receiver with dynamic power adjustment and dynamic adjustment of power consumption of a multi-carrier receiver in order to simultaneously satisfy the system performance and power consumption requirements of the mobile receiver in the OFDM system.

The invention discloses a multi-carrier receiver with dynamic power adjustment, the receiver comprises: a demodulator, receiving a multi-carrier signal; a channel estimator, estimating channel characteristics of each sub-carrier; mutual interference between carriers a detector for estimating mutual interference between carriers; a system performance detector for detecting system performance; a mutual interference canceller between carriers, when turned on, subtracting the demodulated multi-carrier signal from the estimated carrier-to-carrier Inter-interference output, when off, output the demodulated multi-carrier signal; determine the circuit, when the inter-carrier interference exceeds the mutual interference threshold between the carriers and the system performance is less than the system performance threshold, the mutual interference between the carriers is turned on a canceller; and an equalizer that equalizes an output signal of the mutual interference canceller between the carriers according to the estimated channel characteristics.

Another embodiment of the present invention provides a method for dynamically adjusting power consumption of a multi-carrier receiver, including: demodulating a multi-carrier signal, wherein the multi-carrier signal includes a plurality of sub-carriers; and estimating each sub-carrier according to the demodulated multi-carrier signal Channel characteristics of the carrier; estimating mutual interference between carriers from the demodulated multi-carrier signal; detecting a system performance; when mutual interference between carriers exceeds a mutual interference threshold between carriers and system performance is less than a system performance threshold Subtracting the estimated inter-carrier interference from the demodulated multi-carrier signal to obtain a first output signal; and equalizing the first output signal according to the estimated channel characteristics, and according to the equalized multi-carrier signal To update system performance.

The method for multi-carrier receiver with dynamic power adjustment and the power consumption of dynamic adjustment multi-carrier receiver provided by the invention can effectively reduce the average power consumption of the receiver by selectively turning on the mutual interference canceller between carriers .

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Figure 1 is a simplified schematic diagram of a multi-carrier receiver with dynamic power adjustment. The multi-carrier receiver 10 includes a demodulator 102, an ICI detector 104, a system performance detector 106, a decision circuit 108, an ICI canceller 110, and a channel estimator ( Channel estimator 112 and equalizer 114. The multi-carrier signal may be an OFDM signal or a multi-carrier code division multiple access (MC-CDMA) signal, which is received by the demodulator 102. The demodulator 102 can be implemented by Fast Fourier Transform (FFT). The demodulated multicarrier signal is input to the ICI canceller 110, the ICI detector 104, and the channel estimator 112. Channel estimator 112 estimates the channel characteristics of each subcarrier, such as the amplitude and time-derivative of each subcarrier. System performance detector 106 detects system performance. In some embodiments, the system performance may be a signal-to-noise ratio (hereinafter referred to as SNR) or a bit error rate (hereinafter referred to as BER). ICI detector 104 detects ICI (e.g., ICI intensity). The ICI is sent to the decision circuit 108 along with the system performance. The decision circuit 108 turns on the ICI canceller 110 only when the ICI exceeds the ICI threshold and the system performance is less than the system performance threshold. In other words, the ICI canceller 110 is turned off when the ICI is less than the ICI threshold or the system performance is greater than the system performance threshold. The ICI canceller 110, when turned on, subtracts the estimated mutual interference between the carriers from the demodulated multicarrier signal. The resulting signal is input to the equalizer 114 to normalize the signal. The operation of equalizer 114 is dependent on the estimated channel characteristics provided by channel estimator 112. The output of the equalizer 114 is input to the system performance detector 106. In some embodiments of the invention, the ICI detector 104 is a speed estimator, a Doppler frequency estimator, a channel time varying estimator, an ICI cancellation estimator, or any other similar monitoring ICI. Estimator. The system performance detector 106 can be an SNR estimator, a BER estimator, or other estimator that reports the quality of the receiver.

In an embodiment of the present invention, in order to increase the tolerance of the Doppler shift in the action channel, the output of the equalizer 114 is further provided to a forward error correction (hereinafter referred to as FEC). For example, DVB-H specifies the use of MPE-FEC to provide an additional layer of interleaving and error correction to provide a more stable signal in a mobile environment. Figure 2 is a schematic diagram of a DVB-H transmitter. The DVB-H transmitter includes an IP-encapsulator 202, a Reed-Solomon (referred to as RS in the following description) encoder 2011, an outer interleaver 2012, a volume. Convolutional encoder 2013, inner interleaver 2014, mapper 2015, OFDM modulator 2016, digital-to-analog converter (in the figure and below) Referred to as D/A) 2017, and radio frequency front end 2018. The inner interleaver 2014 and the outer interleaver 2012 randomly distribute errors so that the RS encoder and the convolutional encoder in the receiver, such as a Viterbi encoder, can maximize the use of random errors. The IP encapsulator 202 includes a timing-slicing module 206 and an MPE-FEC 204. The time slicing module 206 provides a flexible period and is available for DVB-H services. The time slice period can be as high as 500ms and as low as 50ms. The MPE-FEC 204 provides an additional forward error correction function that allows the receiver to operate under particularly difficult reception conditions. The MPE-FEC frame is set to a matrix having 255 columns and an elastic number column. Figure 3 depicts an MPE-FEC matrix. The number of columns can vary from 1 to 1024 depending on the transmission conditions. Each position in the matrix is a message byte. On the left side of the MPE-FEC frame, there are 191 lines on the far left, which are dedicated to IP datagrams and possible padding, which is called Application data table. The right side of the MPE-FEC frame, including the rightmost 64 lines, is dedicated to the parity information of the FEC code, and is called the RS data table, which contains the RS data and the deleted RS data line. Figure 4 is the layout of the application data sheet. IP datagrams and padding data are included in the matrix of 191 rows and a variable number of columns as described above. The address of each tuple location in the application data table is in the range of 1-191 times the column number. Similarly, the address of each tuple location in the RS data table shown in FIG. 3 is in the range of 1-64 times the column number. By adding the check message calculated from the IP datagram and sending the check message in the separate MPE-FEC section, even under poor reception conditions, no error can be output (error-free). IP datagram (after MPE-FEC encoding). Each MPE-FEC section contains 16 bytes consumed by the header and cyclic redundancy check (CRC)-32. By using the cyclic redundancy check in the MPE-FEC packet header, if the cyclic redundancy check fails, the flag indicates that the MPE-FEC packet content is unreliable. According to the DVB-H standard, time slicing is mandatory in the DVB-H system, while MPE-FEC is optional. The MPE-FEC standard is compatible with non-MPE-FEC adaptive receiver backtracking.

Figure 5a is a schematic diagram of another embodiment of an OFDM receiver with dynamic power adjustment. The illustrated OFDM receiver includes a demodulator 531, an ICI detector 532, a decision circuit 533, a system performance detector 534, a channel estimator 535, an ICI canceller 536, an equalizer 537, and an FEC 50. Figure 5b is an illustration of an embodiment of FEC 50. In Figure 5b, the FEC 50 includes a de-mapper 502, an inner deinterleaver 504, a convolutional decoder 506, an outer deinterleaver 508, an RS decoder 510, and a solution. A descrambler 512, a transport stream de-multiplexer 514, and an IP encapsulator 516. The IP encapsulator 516 includes a time slicing module 518 and an MPE-FEC module 520. In the block shown in Figure 5b, only the MPE-FEC module 520 can be selectively turned on. When receiving an MPE-FEC burst, the IP encapsulator 516 needs to buffer the data with its memory for use in the time interval. For each received segment belonging to the application data table or the RS data table, the IP encapsulator 516 searches the segment header for the start address of the MPE-FEC frame in the segment, and then the MPE-FEC message. The boxes are set to the correct position in their respective tables. After the above procedure is completed, all received bursts can be marked as "reliable" or "unreliable" according to the checksum of the cyclic redundancy check -32. Since MPE-FEC can be omitted, IP encapsulator 516 determines if all MPE-FEC bursts are marked "reliable." If so, the MPE-FEC module 520 remains off to save power. Otherwise, the MPE-FEC module is turned on. The MPE-FEC module 520, if enabled, corrects 64 error bytes in a 255-bit tuple codeword. If there are fewer than 64 unreliable bytes in a column, the MPE-FEC module 520 can correct all errors. If there are more than 64 unreliable bytes in a column, the MPE-FEC module 520 will not be able to make any corrections, so that normally no error correction and output bit errors.

Since the MPE-FEC module and the ICI canceller consume power, selectively turning on the MPE-FEC module and the ICI canceller can effectively reduce power consumption. This will reduce the average power consumption of the receiver. The entire multi-carrier receiver is capable of loading a weak ICI, so there is no need to turn on the ICI canceller when the ICI is weak.

Figure 6 is a flow diagram of a method of dynamically adjusting the power consumption of a received multi-carrier in accordance with an embodiment of the present invention. The method includes the following steps: Step S601: Demodulating a multi-carrier signal; Step S602: Estimating channel characteristics; Step S603: Estimating mutual interference between carriers; Step S604: Detecting system performance; Step S605: Comparing between carriers Mutual interference, system performance and their respective thresholds; step S606: subtracting mutual interference between carriers; step S607: equalizing demodulated multi-carrier signals, updating system performance; step S608: whether MPE-FEC bursting is "reliable"; S609: RS decodes all MPE-FEC bursts.

Beginning in demodulating a multicarrier signal in step S601, wherein the multicarrier signal comprises a plurality of subcarriers. The multicarrier signal can be an OFDM signal or an MC-CDMA signal. In step S602, the channel characteristics of each subcarrier are estimated based on the demodulated multicarrier-wave signal. In step S603, ICI (e.g., ICI intensity) is estimated based on the demodulated multicarrier signal. In step S604, system performance is detected. In some embodiments of the invention, the system performance is SNR or BER. In step S605, the ICI is compared to the ICI threshold and the system performance is compared to the system performance threshold. In step S606, if the ICI exceeds the ICI threshold and the system performance is below the system performance threshold, the estimated ICI is subtracted from the demodulated multicarrier signal. In step S607, the demodulated multi-carrier signal is equalized according to the estimated channel characteristics, wherein the equalized multi-carrier signal is used to update system performance. If the ICI is lower than the ICI threshold or the system performance exceeds the system performance threshold in step S605, the method directly proceeds to step S607. In an embodiment of the invention, the mutual interference between carriers is speed, Doppler frequency, channel time varying or the like.

In some embodiments, the equalized multi-carrier signal comprises 255 MPE-FEC bursts. The MPE-FEC burst is checked in step S608. Each burst is marked as "reliable" or "unreliable". If more than one burst is marked as "unreliable", all 256 MPE-FEC bursts are decoded by the RS in step S609. If all MPE-FEC bursts are marked as "reliable", RS decoding is omitted.

The embodiments are only intended to illustrate the embodiments of the present invention, and to illustrate the technical features of the present invention, and are not intended to limit the scope of the present invention. It is intended that the present invention be construed as being limited by the scope of the invention.

10. . . Multi-carrier receiver

102, 531. . . Demodulator

104, 532. . . ICI detector

106,534. . . System performance detector

108,533. . . Decision circuit

110,536. . . ICI canceller

112, 535. . . Channel estimator

114,537. . . Equalizer

202, 516. . . IP encapsulator

2011. . . RS encoder

2012. . . External interleaver

2013. . . Convolutional encoder

2014. . . Internal interleaver

2015. . . Mapper

2016. . . OFDM modulator

2017. . . D/A

2018. . . RF front end

206, 518. . . Time slice module

204. . . MPE-FEC

50. . . FEC

502. . . Demapper

504. . . Internal deinterleaver

506. . . Convolutional decoder

508. . . External deinterleaver

510. . . RS decoder

512. . . Unmixer

514. . . Transport stream demultiplexer

520. . . MPE-FEC module

S601-S609. . . step

Figure 1 is a simplified schematic diagram of a multi-carrier receiver with dynamic power adjustment.

Figure 2 is a schematic diagram of a DVB-H transmitter.

Figure 3 depicts an MPE-FEC matrix.

Figure 4 is the layout of the application data sheet.

Figure 5a is a schematic diagram of another embodiment of an OFDM receiver with dynamic power adjustment.

Figure 5b is an illustration of an embodiment of the FEC of the receiver shown in Figure 5a.

Figure 6 is a flow diagram of a method of dynamically adjusting the power consumption of a received multi-carrier in accordance with an embodiment of the present invention.

10. . . Multi-carrier receiver

102. . . Demodulator

104. . . ICI detector

106. . . System performance detector

108. . . Decision circuit

110. . . ICI canceller

112. . . Channel estimation

114. . . Equalizer

Claims (21)

A multi-carrier receiver with dynamic power adjustment, comprising: a demodulator receiving a multi-carrier signal, wherein the multi-carrier signal comprises a plurality of sub-carriers; and a channel estimator estimating from the demodulated multi-carrier signal Measuring the channel characteristics of each subcarrier; a mutual interference detector between carriers, estimating the mutual interference between one carrier of the mutual interference between the carriers from the demodulated multi-carrier signal; a system performance detector, detecting Measuring system performance; a mutual interference canceller between carriers, when the mutual interference canceller between the carriers is turned on, subtracting the demodulated multi-carrier signal from the estimated inter-carrier interference output, when the carrier is When the mutual interference canceller is turned off, the demodulated multi-carrier signal is output; a determining circuit is turned on when the mutual interference between the carriers exceeds a mutual interference threshold between carriers and the system performance is less than a system performance threshold. a mutual interference canceller between the carriers; and an equalizer that equalizes mutual interference between the carriers according to the estimated channel characteristics The output signal, wherein said other of the multi-carrier signal to the above-described detector system performance for updating the system performance. The multi-carrier receiver with dynamic power adjustment according to claim 1, wherein the determining is when the mutual interference between the carriers is less than a mutual interference threshold between the carriers or when the system performance exceeds the system performance threshold. The circuit turns off the mutual interference canceller between the above carriers. Dynamic power adjustment as described in item 1 of the patent application scope The multi-carrier receiver further includes a multi-protocol encapsulation-forward error correction module, wherein the equalized multi-carrier signal comprises 255 bursts, and each of the bursts is marked as "reliable" or "unreliable". If all 255 of the above bursts are marked "reliable", the multi-protocol package-forward error correction module remains off to save power, otherwise the multi-protocol package-forward error correction module is turned on. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the demodulator is implemented by a fast Fourier transform. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the system performance detector is a signal noise ratio estimator, and the system performance is a signal to noise ratio. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the system performance detector is a one-bit error rate estimator, and the system performance is a one-dimensional error rate. The multi-carrier receiver with dynamic power adjustment according to claim 1, wherein the mutual interference detector between the carriers is a speed estimator, and the mutual interference between the carriers is the multi-carrier receiver. Speed. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the mutual interference detector between the carriers is a Doppler frequency estimator, and the mutual interference between the carriers is The Buhler frequency is expressed. A multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the mutual interference detector between the carriers is a pass The time-varying estimator, and the mutual interference between the above carriers is represented by a channel time varying. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the multi-carrier signal is an orthogonal frequency division multiplexing signal. The multi-carrier receiver with dynamic power adjustment as described in claim 1, wherein the multi-carrier signal is a multi-carrier code division multiplexing multiple access signal. A method for dynamically adjusting power consumption of a multi-carrier receiver includes: demodulating a multi-carrier signal, wherein the multi-carrier signal includes a plurality of sub-carriers; and estimating a channel of each sub-carrier according to the demodulated multi-carrier signal Characteristic; estimating the mutual interference between one of the inter-carrier interferences from the demodulated multi-carrier signal; detecting a system performance; when the mutual interference between the carriers exceeds a mutual interference threshold between the carriers and the system performance When less than a system performance threshold, subtracting the estimated inter-carrier interference from the demodulated multi-carrier signal to obtain a first output signal; and equalizing the first output signal according to the estimated channel characteristic, And updating the system performance according to the above-mentioned equalized multi-carrier signal. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the mutual interference between the carriers The demodulated multi-carrier signal is equalized when the interference threshold between the carriers is less than or the system performance exceeds the system performance threshold. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the equalized multi-carrier signal comprises 255 bursts, each of which is marked as "reliable" or "not" Reliable, and the above method further includes Reed's trick to decode the above 255 bursts when more than one burst is marked as "unreliable". A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the system performance is a signal to noise ratio. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the system performance is a one-bit error rate. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the mutual interference between the carriers is represented by the speed of the multi-carrier receiver. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the mutual interference between the carriers is represented by a Doppler frequency. A method for dynamically adjusting the power consumption of a multi-carrier receiver as described in claim 12, wherein the mutual interference between the carriers is represented by a channel time variation. The method for dynamically adjusting power consumption of a multi-carrier receiver according to claim 12, wherein the multi-carrier signal is an orthogonal frequency division multiplexing signal. A method for dynamically adjusting power consumption of a multi-carrier receiver as described in claim 12, wherein the multi-carrier signal is a multi-carrier code division multiplex multiple access signal.